


Laced with Love

by MarshmarrowSans



Series: Tumblr Requests [9]
Category: Undertale (Video Game)
Genre: And a whole lot of skeletal anatomy terms, Dom/sub, Ecto-Penis (Undertale), Established Relationship, F/M, Femdom, Fluff, Fluff and Smut, Plot What Plot/Porn Without Plot, Sacrum Lacing, Smut, Sub Sans, but also a fuckton of love and praise, dom reader, slight degradation
Language: English
Status: Completed
Published: 2018-04-14
Updated: 2018-04-14
Packaged: 2019-04-22 23:47:36
Rating: Explicit
Warnings: Creator Chose Not To Use Archive Warnings
Chapters: 1
Words: 3,769
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/14319741
Author URL: https://archiveofourown.org/users/MarshmarrowSans/pseuds/MarshmarrowSans
Summary: Ever since you started dating Sans, your life has been an ongoing, interactive skeletal anatomy course.Sometimes, that results in some interesting experimental things in the bedroom.  Like getting acquainted with a lovely little part of his body called his sacrum.





	Laced with Love

**Author's Note:**

> Yup-- I got a request for a sub Sans sacrum lacing fic a long, long time ago and finally got around to filling it.

Sans’ tailbone was sensitive in the best and worst of ways. That was one of the first things you learned in your relationship with him, and you learned it the hard way. A well-meaning slap on the ass made him yelp in pain, put his hands over it, and stare you down like a kicked puppy. You felt really bad about that, but not so bad about the gentle caresses you paid it in the bedroom ever since, once you realized that, if you used light touch, it was quite an erogenous zone for him.

 

With that figured out, playing with his sacrum wasn’t a big step away. It was a small step upwards, to be exact, and it seemed to be almost as sensitive. You’d been testing the waters there for awhile—the last few times the two of you had sex, you let your fingers trace over those little gaps in his bones, and as you did, his body had arched blissfully against yours.

 

Funny as it was, you got your idea while lacing up a pair of badass military boots to go with a particularly sharp-looking outfit. Poking the shoelace through the holes, pulling them taut in little criss-crossing patterns, the thought occurred to you…  


… Wouldn’t he look just gorgeous with little patterns just like that weaving through his bones?

 

You didn’t want to use a shoelace for that, of course. You wanted something prettier. After awhile of browsing your local fabric store, you bought a stretch of sapphire blue, silk ribbon that he probably assumed, when he saw it placed so innocently on your nightstand, was for your hair. It sat there unassumingly, for a few nights in a row, until you finally managed to get your lazy boyfriend in the mood for that special kind of physical affection with an energy demand.

 

He didn’t even realize that you’d picked it up at first. He was far too absorbed in kissing you, pulling you closer and closer until the warmth of your body and your pounding heartbeat felt so strong they could overpower his senses, cradling your cheek at first, then every other round, soft part of your body. His eyes were closed most of the time, and in those small moments that he looked at you with half-lidded eyes, they were entirely focused on your face. You were forced to draw his attention to your little change of plans.  
  
”Sans.”  
  
His eyes blinked open fully, and he stopped kissing you for a moment, his wandering hands coming to rest where they’d been at the moment you spoke—your chest. His jacket was unzipped, pushed to either side of his body, showing off his ribs and thus the fact that he hadn’t been wearing a T-shirt under it today. His cheeks were dusted blue, his expression downright dreamy, as if high off nothing but the feeling of kissing you. God, he was already a sight to behold.   
  
”yeah, babe?”

 

You didn’t say anything quite yet. You smiled at him mischievously and stretched the ribbon between your hands, wondering if he would pick up what you were putting down.

 

“… whassat?”  
  
Maybe not.  
  
”you wanna tie me up like when you used that vibrator on me? ‘cause i’m down for it but with all due respect, you might wanna use something longer than that.”

 

You shook your head from side to side, the smile never leaving your lips. “ _Lacing_ might be a more accurate term. I’m going to _lace_ you up.”

 

He quirked a brow bone at you. “lacing. which is just. tying but pretty?”

 

“Honey. When I’m done with you? You are going to look _very_ pretty.” You loved being cheeky and all, but for clarity and for the sake of his informed consent, you told him. “I couldn’t help but notice those perfectly symmetrical holes you’ve got on your sacrum. And you seemed to like it when I played with them with my fingers. So I thought I could lace it up with this. Tie it up with a cute little bow. What do you say?”  
  
How cute. His blushing had progressed from a light dusting on his cheeks to a noticeable hue all the way down to his shoulders. “oh. uh. s-sure. but. it’s because you’re into it, right? haha, ‘cause. ‘cause i understand the need for a good joke, but i don’t wanna be the _butt_ of it, you feel me?”

 

You rolled your eyes at him and gave him a pity chuckle for that pun. “Yes, Sans. I’m taking this seriously. Or at least as seriously as I can take it with you, punmaster.” You gave him a playful nudge on the cheek with your fist, which he turned his head a little to compensate. Seeing his acceptance, you felt your heart beat a little faster. He was a bit of a smug bastard in his everyday life. So mellowed out, so self-assured. Bulletproof. Seeing him come undone in the bedroom, just for you, like you were sure he was about to do tonight, was absolutely intoxicating. You made a circling motion in the air with your finger. “In that case. I want you on your hands and knees.”

 

He was never one to disobey you once you established your dominance. He did what you asked, though in that characteristic slow and lazy way of his. He turned on his side, as if trying to find a comfortable position in his sleep, then on his stomach, then pulled up his knees so they were supporting his weight and braced himself with his hands on the mattress. He already looked so irresistible, obeying you and offering himself to you like that, that you could feel your arousal building, and that was always enough to kick your sexual confidence into gear.

 

“Good boy,” you praised him in a sweet coo, momentarily taking over that coveted role of smug bastard in this relationship. You found the shape of his tailbone through his short, ran your fingers in a V shape on either side of it, then followed it up to his sacrum. You lingered there, meaningfully, hyperfocusing on your lover’s irregular breathing, and the heat and movements of his body. He reacted, with a gasp or a tiny shift in his position or both, every time you touched something new, and even when you went back and retraced some things that had prompted an especially strong reaction the first time. You could imagine, twenty years from now, you would have a map of his body burned into your brain showing all the places that he liked to be touched the most.

 

“You’re already so friggin’ cute like this, Sansy. You want it so bad, don’t you?”

 

He tensed, clearly embarrassed to be speaking of his own desires so frankly, but he wasn’t about to lie to you. “yeah. what’m i supposed to do, _not_ get excited when my drop-dead gorgeous girlfriend comes home and starts smooching me all over?”

 

He relaxed a little and let out a long, soothed breath once you got past the lower regions of his spine and began massaging him, intervertebral space by intervertebral space, through his jacket, all the way up to the area between his scapulae. Once you were there, you found yourself looming over him, and you took the opportunity to push down on his upper body. He let out a soft, nervous noise that you could hardly believe came from the same bass-voiced man you knew, but he certainly didn’t put up any resistance. He crumpled obediently so that he was supporting himself with his forearms now, forehead resting on your pillow. You took the last step and pulled his hips so that his backside was raised up high in the air, just how you wanted it.

 

Now, you lacked the equipment to do any sort of penetration, but that didn’t stop you from grinding your crotch against his raised backside and purring to him, “You’re the drop-dead gorgeous one. You should just see yourself right now.” Lying prone, face in the pillow, ass raised in the air, blushing blue from the top of his skull down past where the hood of his jacket covered his neck. His spine must be arching beautifully to accomplish that…

 

“no thanks. i think my boner would die,” came his muffled voice.

 

You giggled at his comment, but you could understand. As confident in your sexuality as he made you feel, you still didn’t much like the idea of seeing yourself during sex. Only your partner. “Then I promise not to hold a mirror up. Now try and hold still.”

 

You slipped your hands down either side of his shorts, pausing for a moment to show your admiration for his broad pelvic bones through the light caressing of your fingers, then pulled his shorts down slowly. This was a show for you, and you were taking in every moment. The intricate ridges and grooves of his sacrum and coccyx. The way his bones became more smooth and regular past there, from his femurs to his tibia and fibula. He had to lift his knees a little for you to get there, but you left his shorts around his ankles for now. Finally, his sacrum was completely available to you.

 

“Damn. It really is a huge shame you can’t appreciate this like I do, though. You’re perfect. There’s no other word for you. Just perfect.” With your hands still on his hips, you leaned over him to kiss the back of his skull. He almost sounded like he purred when you did that, and in his bliss, you felt him shift and willingly raise his butt a little higher for you.

 

“Mmm. You’re such a willing little pet. I like this,” you chuckled as you pulled away. “And now I’m going to do the impossible—“ you stretched the silk ribbon between your hands—“and improve on perfection.”

 

You’d decided on a cute but simple criss-crossing pattern. You didn’t want to be fumbling around in the middle of foreplay and having to go look at the guide again for how to do something especially intricate like those lattice or checkerboard patterns that you saw. This one, unlike those, was easy to memorize, so you were able to make quick work of it. From the moment you slid the ribbon through the first hole, you could tell Sans was struggling to stay still like you told him to. You weren’t about to punish him for that—you had no idea what it was like for him, as a skeleton, to have his sacrum laced. It gave you pause for a moment, purely because you were concerned you might be hurting him, but the needy groan in his throat when you pulled the first criss cross taut was anything but pained.

 

“How you feeling, cutie?” you asked, though you didn’t pause before continuing with the next two holes.

 

“fffuck…” he whispered, breath as warm as his magic-flooded bones.

 

“You’re feeling fuck.” You giggled, despite yourself. “Good fuck?”

 

“ _best_ fuck.”

 

Perfect. You pulled the second section even tighter than the first, emboldened by his reassurance, and you got your payoff in the form of him cussing under his breath and melting under your touch. You almost felt like you were holding up his hips with the ribbon you were lacing him up with.

 

“Just be patient, baby. Just one more. Then I’ll take care of you.”

 

“please…” That was all he got out, but you knew what he meant. How badly he wanted you to take care of his aching arousal. Just because he hadn’t formed his ecto-cock yet didn’t mean that the excited magic rushing through his body wasn’t enough to give him that physical need for you. On the contrary—while a human like you might feel that characteristic, localized throbbing in your groin, he felt it all over, at least until he concentrated his magic into your favorite little magical appendage of his. Making him wait, forcing him not to focus that need into one central organ, but to feel it all over… it was one of your favorite methods of holding your dominance over him.

 

He was panting softly, swallowing nothing, and moaning each time he did by the time you were finished pulling the two ends of the ribbon through the last two holes. Perfect. You had just enough of the ribbon left to tie it off in a bow. That part was even more quick and easy than the rest, and you could practically feel the anticipation in his body once the sliding and tugging stopped. Satisfied with the tension and alignment of the ribbon, you let out a content sigh and sat back to admire your handiwork.

 

Sans was the most beautiful mess you’d ever seen. That applied both to your everyday life together and to this moment. Presenting himself to you like a cat in heat, hot and blushing with arousal and embarrassment, shorts around his ankles, all laced up like your personal little birthday gift with a ribbon the color of his soul. You shook your head in near disbelief, love for him flooding your heart and soul simultaneous to the blood rushing to your genitals.

 

“Look at you. All laced up. All for me. Absolutely beautiful.”

 

“th… thanks, babe.”

 

“You don’t have to thank me for telling you the truth! I want to hold on to this moment forever.” You paused for a moment. Honestly, it wouldn’t be the first time Sans let you take a picture of him in a compromising position. But it would certainly be the most compromising of the positions he’d let you photograph him in. You reached for your phone. “So. Am I allowed to take pictures of the artwork in this gallery?”

 

“i mean. it’s _your_ artwork.” Whether he was referring to the fact that you’d laced the ribbon through his sacrum or referring to himself as yours, you couldn’t tell. You hoped it was both. “just. uh. don’t show anyone?”

 

“Of course not. Like you said. It’s my artwork. For my eyes only.” You smirked, centering him in frame. “Perfect. Just like that. Say cheese, gorgeous.”

 

He didn’t lift his head from the pillow, emphasizing the futility of such a request. “babe. you’re so cheesy.”

 

“I know.” You took the picture and set your phone aside. Another shot for your growing collection of photos for a rainy day. It was a good thing Sans wasn’t very camera shy. “Now. Just like I promised. I think you’ve more than earned a little compensation. You’ve been so sweet, and good, and obedient…” You moved your body over his, fit it against his as best you could given that he was so much shorter than you, and you ended up with your chin at the top of his head.

 

He hummed happily as your body pressed into his and finally allowed him to lower his hips back to comfortable position. “of course. anything for you, doll.”

 

“But I bet you wanted release so bad. Bet you wanted me to be done with it, let you form your stiff little cock and take care of you already.”

 

“… you’re not wrong.”

 

“Eager little whore.” You definitely had to get him in the right mood before you started saying things like that, but this was the right mood if ever it existed. His blush grew a bit more noticeable, and he trembled underneath you. “But I can’t blame you for what you want. You were a very, very good boy. Loyal, obedient, patient. So…” You smiled, reaching around and stimulating the center of his pelvis with your fingers. There was a ridge there, right where he formed his cock, that was just as sensitive as his tailbone and sacrum. He crumpled and made a choked sobbing noise when you touched it. “I’ll reward you.”

 

“baaaabe…”  
  
”You don’t have to whine like a friggin’ baby.” You kissed the back of his skull and let your voice soften. “I’m right here and I’ll take good care of you. I always take good care of you, don’t I?”

 

“you do. you always do.” There wasn’t a trace of uncertainty or hesitation in his voice. He knew that as a fact.

 

“Go ahead.”

 

You moved your hand away, even lifted yourself off of him and sat back on your legs, to give him a moment to form his overexcited magic into his luminous blue length. It was as mouth-wateringly short and thick as ever, and it made your pussy throb to think about all the times it had been inside you, or in your hand, or between your lips. You had your pick of the litter here as to what you wanted to do with it—you were sure he would take any option right now with boundless enthusiasm.

 

Looking at him, you realized that the best way to keep his cute little laced up sacrum in your view was probably the middle option.

 

“Awh. Look how excited you are,” you praised him in a sugar-sweet voice. “You must be close, huh?”

 

“heheh. uh, quickie?” he suggested nervously. Sometimes he joked about how long—or rather, how short—he lasted in the bedroom, and sometimes he seemed genuinely self-conscious about it. His expression put him right in between those two extremes. Playful, but nervous, as if just waiting to hear your disapproval.

 

“No. Don’t worry about me. I had my fun.” You hooked your finger under the ribbon you’d laced his sacrum with and gave it a slow, firm pull. It shifted through every hole in his sacrum at once, he jerked in your arms as if startled, and he whined somewhere deep in his throat at the sensation. With your other hand, you reached around and gripped his cock, giving it a couple of firm strokes before finding the tip with your thumb and rubbing his precum in a gentle circle there.

 

“Gorgeous,” you praised him in that husky whisper that sent chills down his spine. “You’re fucking gorgeous when you’re needy like this, Sans. I want you to cum for me. Hard. All over my hand, yourself, the bedsheets. Like the hot, dirty little slut you are.”

 

“oh, _fuck_ …” You weren’t moving your hand much, but he compensated by moving his hips forward and backward, so your hand moved up and down his cock. You chuckled at his little effort. Cute.

 

“Look at you. Lazy bones isn’t so lazy now, is he? Mmm.” You gave him what he wanted—you held his cock firmly in your hand and pumped it at a quick, steady, enthusiastic pace. Much faster than he could’ve done just by moving his hips. He gave up control completely to you, and he’d never seemed happier to hide his face in the pillow. His body bounced gently with the rhythm of your hand, as did his voice as he verbalized his approval of what you were doing for him

 

“oh. babe. _fuck_. **_yes_**.”

 

You couldn’t help it. His submission, his low, excited voice, his appearance, it was all such a turn-on for you. You let go of the ribbon, spread your legs, slipped your hand between them, and paid yourself a little attention, too. You were soaking wet, and used it as lubrication on your engorged clit.

 

“please, baby—faster—i’m so damn close—“

 

With pleasure. You increased your pace, both on yourself and on him. His bones rattled a little bit each time your fist slid back to the base of his cock and hit his pelvis.

 

“oh, stars. i love this _so much_. i love you. i love you, _i love you, **i love you, i**_ —!“

 

He went off like a gunshot on the last syllable. In one moment, his voice devolved into a growl deep in his chest, and in the next, it crescendoed to a startled and impassioned cry of release. At the height of his climax, he screamed your name. It was a beautiful sight to see—your skeletal lover was so overwhelmed with bliss. His ejaculate came in a series of powerful spurts that quickly coated your hand, his femurs, some of his jacket, and some of the sheets underneath him, and all the while, he whined and whimpered as he let the rest of his climax wash over him.

 

It pretty much went without saying that you followed soon after. Seeing Sans lose himself in the moment sent you completely over the edge. With an ecstatic yelp of your own, you shoved your fingers deep into your pussy and used your thumb to resume your work on your clit. The pleasure was of great enough magnitude to curl your toes and make your knees weak. You collapsed on him, then wrapped an arm around him and pulled him so that he was lying on his side with you spooning him from behind. Both of you were left breathing heavily. It had been one of those sessions. You stopped jerking him off as soon as his body went slack, but you kept your hand wrapped around his cock until he silently let the magic concentrated there dissipate back into his body.

 

“… shit, babe. i’m, uh, kind of lying in my own cum right now.” He laughed, clearly not too bothered by it, and you giggled along with him.

 

“Oops. I just kind of—hhhhh—pushed you down into it, didn’t I?”

 

“heheheheh! yeah-haha.” God, the post-sex giggles always got you two. Despite the mess, he made no move to get out of bed. “lemme guess. laundry day tomorrow?”

 

“Laundry day tomorrow.” You stuck your tongue out and wiped your hand off on his jacket, now that that was established. “Your fault.”

 

“uh. excuse me? _your_ fault. this dick didn’t stroke itself.”

 

“Truuue.  But if I didn’t have such a gorgeous man in my bed, I wouldn’t have had anything to stroke, now would I?”  
  
”alright.  it was a team effort.”

 

“Sex generally is.”

 

Sans let out a content sigh, and so did you.  Despite the existence of orgasms, this was always the nicest part.  There was no feeling quite like the afterglow, nothing quite like lying together in the near-silence, watching your lover’s chest rise and fall with breaths he didn’t even need to take.

 

A few minutes later, you tried telling him that you loved him.  But all you got in response was a long, low snore.

 

Oh well.  He’d said it, like, five times in bed, and he always said it again first thing in the morning. You could let him sleep and wait until then.

**Author's Note:**

> I don't know who requested this but thanks for making me realize I'm into something I didn't know I was into before. Brb, boutta rub one out to Sans with his sacrum laced.


End file.
